This application claims the benefit of German patent application DE P 10124832.6 filed May 22, 2001, herein incorporated by reference.
The present invention relates to a yarn splicing device for producing a knot-free yarn connection in a spicing channel of a splicing body and, more particularly, to a splicing device adapted for splicing an elastic yarn.
Such yarn splicing devices commonly comprise a splicing body formed with a splicing channel for receiving an upper yarn and a lower yarn to be spliced with one another and at least one inlet opening into the splicing channel for injecting compressed air thereinto for pneumatically splicing constituent fibers of the yarns. Respective clamping devices clamp the upper yarn adjacent one end of the splicing channel and the lower yarn adjacent an opposite end of the splicing channel. Likewise, respective cutting devices cut an end of the upper yarn to a defined length adjacent the opposite end of the splicing channel and cut an end of the lower yarn to a defined length adjacent the one end of the splicing channel. A preparatory nozzle adjacent the upper yarn cutting device prepares the end of the upper yarn for splicing and pneumatically holds the upper yarn end while being prepared, and a like preparatory nozzle adjacent the lower yarn cutting device prepares the end of the lower yarn while pneumatically holding it.
Such yarn splicing devices are described, e.g., in German Patent Publication DE 40 05 752 A1 or DE 44 20 979 A1. The attempt is being made to adapt pneumatic yarn splicing devices to a growing range of threads and yarns in order to be able to produce knot-free connections with great tensile strength and a good appearance for all applications. These yarn connections should differ as little as possible from the tensile strength and the appearance of the main length of the thread or yarn. The pneumatic splicing is carried out in a splicing channel or conduit. The yarns to be connected are placed into this splicing channel in opposite directions and in an overlapping manner. The yarn ends are subjected in preparatory nozzles, also called opening tubes, to a suitable pneumatic or pneumatic/mechanical pre-treatment for the opening and parallelization of their constituent fibers. The yarn ends are subsequently intermingled in the splicing channel of a splicing body, that is designated in German Patent Publication DE 44 20 979 A1 as a splicing head, with the aid of compressed air to a knot-free yarn connection. Such a splicing can achieve approximately the same yarn strength as the main length of the yarn and represents an almost yarn-like connection of two yarn ends. The time of the actual splicing process is usually approximately 15 to 40 ms, depending on the particular splicing conditions.
Presently, elastic and highly elastic yarns, e.g., for socks, underwear and sports clothing, are being processed to a great extent. These yarns frequently comprise a highly elastic core yarn whose material consists, for example, of spandex fiber. Elastic and highly elastic yarns can cause significant problems during the splicing process. Defective splices or even no splice connection frequently occur. The cause of this resides in the elastic behavior of the yarn in the yarn splicing device.
After a yarn break the so-called upper yarn is grasped by a pivotable suction nozzle and placed into the yarn splicing device in a tensioned state by pivoting the suction nozzle. The same process is used with the so-called lower yarn. Both the upper yarn and the lower yarn are clamped under tension in a clamping device and their ends are severed by a cutting device. In order to draw the yarn ends into the adjacent preparatory nozzles by suction immediately after the cutting and to hold them there until the actual splicing process, compressed air is usually blown into the preparatory nozzles before the cutting action, which air is directed away from the mouth of the preparatory nozzles onto the yarn end and produces a suction action. In the case of elastic and highly elastic yarns, the contractive relaxation of the elastic yarn end when freed by the yarn cutting action is so great that the yarn ends are no longer held by the suction draw in the preparatory nozzles and may possibly even be drawn entirely out of the preparatory nozzles. This hinders or prevents the preparatory opening of the yarn ends as well as the subsequent splicing process. Unsuccessful splicing attempts and therewith repetitions of the entire yarn connecting process occur. The suction action exerted by the preparatory nozzles can not be reinforced as desired in order to increase the holding power since this, on the one hand, causes a greater consumption of compressed air, which is undesired for economic reasons, and on the other hand, can result in an adverse effect on the quality of the splice. As is known, a substantially more protective, better and more uniform opening of the yarn ends takes place at rather low pressures of the preparatory air.
The described deficiencies can not be eliminated with the known yarn splicing devices existing in accordance with the present state of the art.
Thus, the present invention seeks to address the problem of improving the known yarn splicing devices to enable them to reliably splice elastic yarns.
The present invention addresses this problem by providing a yarn splicing device of the type described above with restraining devices arranged between each yarn clamping device and its associated yarn preparatory nozzle for pneumatically retarding the contraction of elastic yarn ends up to the yarn preparatory nozzles after cutting of the yarn ends.
In this manner, the contraction of the elastic yarn ends is sufficiently reduced and the withdrawal of the yarn ends from the preparatory nozzles is successfully counteracted by the restraining devices acting pneumatically on the yarn between the clamping devices and the preparatory nozzles. The preparation of the yarn ends for splicing and the splicing process itself are no longer disturbed or prevented by the yarn contraction. Standstill times caused by repetitions of the splicing process are avoided. Bulky, additional mechanical clamping devices in the area of the splicing body are not necessary. The action of the restraining device begins extremely rapidly upon actuation. Standard yarn consisting of different raw materials that are wound instead of elastic yarns on a work site in accordance with the invention can be processed without disadvantage as regards the yarn joining process or the quality of the yarn connection.
The restraining devices are preferably arranged between the splicing body and the preparatory nozzle. Compared with an alternative design in which the restraining device is arranged between the splicing body and the clamping device, thus creating more space for the restraining device, there is less play available given the selection of the position of the restraining device, but the contraction of the stretched yarn can be shortened to an especially great extent.
The restraining device is preferably designed as a suction nozzle comprising elements that prevent the drawing in by suction of the yarn end. This reliably avoids the situation that the yarn end can be drawn out of the preparatory nozzle by the drawing in by suction of the yarn end into the restraining device. This can be brought about in an advantageous manner by a tubular suction nozzle with an air-permeable cover on the suction intake. A design of the cover as a grate with grate rods running largely transversely to the path of the yarn, together with the tensioning of the yarn caused by the preparatory nozzle, prevents the drawing in of the yarn into the restraining device and acts preventively against a clogging of the cover, as can readily occur with a wire mesh. If the control device associated with the yarn splicing device is set up in such a manner that it continuously activates the restraining device at the latest during the cutting of the yarn and up to actuation of the splicing device, a reliable course of the splicing process is assured.
If the preparatory nozzle and the restraining device are connected at the same time to a source of compressed air, the control expense is especially low since no switching times that differ from one another must be observed. The loading of the preparatory nozzles and of the restraining device with compressed air for the injection of air and to produce the particular suction effect can take place with a single, joint switching process. The preparatory nozzle and the restraining device can be connected to the same source of compressed air, which permits an especially simple construction as regards compressed-air lines and switching elements. Alternatively, the preparatory nozzle and the restraining device can be connected to two sources of compressed air with different strengths, which makes a controlling of the holding power of the restraining device readily possible. In another alternative embodiment the restraining device can be connected to a vacuum source in order to produce the suction action.
A friction surface is advantageously arranged adjacent to the restraining device in such a manner that the yarn rests on the friction surface when the restraining device is actuated. This supports and increases the restraining action on the yarn without any damage being caused to the yarn.
The yarn splicing device in accordance with the present invention can also be used in open-end spinning machines. As is known, it is also customary in such textile machines to prepare the yarn end in an appropriate preparatory nozzle before the new spinning start.
The invention permits the desired quality of the splice to be observed and the number of unsuccessful splicing attempts to be lowered. This achieves an increase in the yarn quality and in the productivity of the winding head and of the entire textile machine.
The present invention will be further explained in detail with reference to exemplary embodiments shown in the accompanying drawing figures.